Should the underline be connected to that of \underline{Shorter info}without showing a break? Note that \underline is put below the depth of its contents. Since Shorter info contains no descenders, it will be placed higher than that of Longer info.
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WernerJun 8 '12 at 16:02

Werner, underline height doesn't matter. The break in line after underline{Shorter info} is not desirable.
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Victor ProonJun 8 '12 at 17:04

The reason why this works is because Person1 is similar in width to Person2. If this is not the case, you can always use an extra tab marker \= to identify this location.

\rlap allows for a right overlap (of width 0pt), while \hphantom only takes the horizontal width into consideration (without typesetting anything). That is, no height, and therefore also no descenders. If you have descenders within Shorter info, a regular \phantom should suffice.

Here's an alternative view on something similar, this time using tabular:

You even don't need tabbing in this soolution. But you have to edit in 2 more places to change prson1's info. I thought that maybe there is a way to autpomatically fill those gaps using tabbing..
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Victor ProonJun 8 '12 at 16:59

@VictorProon: I know, hence my statement about the width of Person1 and Person2. I've added an alternative using tabular. Not entirely sure about the context of your usage, so these are just suggestions.
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WernerJun 8 '12 at 17:10

thanks, looks like the second way works the way i want.
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Victor ProonJun 8 '12 at 17:40